The present invention relates generally to inhibitors of arginase and their use for the treatment of pathological states. Two isoforms of arginase have been identified to date, arginase I (ARG I), that is expressed in the cytosole and arginase II (ARG II), that is expressed in mitochondria. The arginase enzymes together with the nitric oxide synthase (NOS) enzymes play an important role in regulating the levels of nitric oxide in cells and in the development of pathophysiological disease states.
The arginases are implicated in various pathological states. These include without limitation erectile dysfunction, pulmonary hypertension, hypertension, atherosclerosis, renal disease, asthma, T-cell dysfunction, ischemia reperfusion injury, neurodegenerative diseases, wound healing, and fibrotic diseases. Although the mechanism of action of arginase enzymes in these disease states is still a subject of ongoing research, several studies imply that the arginase enzymes are often upregulated during pathological disease states.
For example, it is postulated that upregulation of arginase activity results in reduced levels of arginine which in turn reduces the level of nitric oxide (NO) a physiologically important signaling molecule that is required for cell division, arterial vasodilation, regulation of blood flow and for controlling muscular and neurological signal transduction.
In addition to its role in regulating nitric oxide (NO) levels, arginase also affects production of critical polyamines such as putrescine, spermidine and spermine. As arginase catabolizes L-arginine it produces ornithine. Ornithine is subsequently converted to putrescine, spermidine and spermine via ornithine decarboxylase, spermidine synthase and spermine synthase respectively. Thus, the arginase enzymes control physiological signaling events by controlling the intracellular levels of polyamine signal transducers. See Wang, J-Y; and Casero, Jr., R. A., Ed; Humana Press, Totowa, N.J., 2006. Ornithine also provides an alternative biosynthetic pathway to proline and thereby supports collagen production (Smith, R. J.; Phang, J. M., The importance of ornithine as a precursor for proline in mammalian cells. J. Cell. Physiol. 1979, 98, 475-482. Albina, J. E.; Abate, J. A.; Mastrofrancesco, B. Role of ornithine as a proline precursor in healing wounds. J. Surg. Res. 1993, 55, 97-102.)
Given the role of arginase in various pathological states, the present invention provides Formula I and Formula II compounds as inhibitors of arginase activity, as well as methodologies for using the inventive compounds as therapeutics.